This invention relates to thermoplastic polymers which are useful in molding plastic materials for contact with body fluids. More particularly, it relates to a thermoplastic polymer composed of block radial polymers of the diene-aryl substitued olefin butadiene-styrene type which have blended with them certain polymeric materials to form a plastic composition having a high degree of elasticity and resealability so as to be useful as puncturable reseal units in parenteral administration equipment as well as in containers for materials intended for administration to the body.
Recently, radial block polymers of the butadiene-styrene type have been of particular interest in that they display high tensile strength without vulcanization or filler reinforcement. In U.S. Pat. Nos. 3,281,283 and 3,078,254, a process of making such radial block copolymers is described. Further, particular blends of vulcanized butadiene-styrene block copolymers are indicated in U.S. Pat. No. 3,646,161. In U.S. Pat. No. 3,562,355, a mechanical blend of a butadiene-styrene copolymer is described in combination with a polyester urethane. The prior art nowhere describes a blend of nonvulcanized radial block copolymers of the butadiene-styrene type wherein the butadiene-styrene amounts are of a certain quantity and when combined with certain polymeric materials will form a plastic composition having a sufficient elasticity and resealability so that they are readily adaptable for use in composing plastic closure materials having reseal properties for contact with fluids to be administered to the body. In addition, the prior art nowhere describes a plastic composition which is readily suitable for use in the medical plastics field which will have sufficiently low alkaline extraction nephelos values so that ingredients in the composition are not extracted in with the fluids to be administered after contact with the closure material.
It is an advantage of the present invention to provide a novel blend of radial block copolymers of the butadiene-styrene type with other polymeric materials. Other advantages are a thermoplastic composition of the radial block copolymer type which have a high degree of elasticity and resealability so that they can be employed as a pharmaceutical sealing component such as resealable injection sites in parenteral administration equipment without coring, a novel radial block copolymer mixture which can be readily molded, extruded and otherwise processed by customary processes, a thermoplastic material which is compatible and can be sealed or otherwise connected to other types of plastic materials in a parenteral administration set, a novel plastic composition which is compatible with the usual plasticizers, fillers, chelators, lubricants, etc., which are necessary in the fabrication of plastic materials.